Position or displacement sensors are known generally and have been used for many years to measure the movement of a surface. Such a movable surface may be a part of a sensor of the type in which the amount of displacement reflects a variation in a physical condition, such as temperature, pressure, or the like. Often the precise location of the condition to be sensed is in a hostile environment of temprature extremes, or pressure extremes, or both. In such an environment many sensors do no have the ruggedness and durability for extended operation while maintaining a high degree of accuracy.